N-channel bipolar power semiconductor device with p-layer in the drift volume

ABSTRACT

A power semiconductor device having a semiconductor body configured to conduct a load current is disclosed. In one example, the device includes a source region having dopants of a first conductivity type; a semiconductor channel region implemented in the semiconductor body and separating the source region from a remaining portion of the semiconductor body; a trench of a first trench type extending in the semiconductor body along an extension direction and being arranged adjacent to the semiconductor channel region, the trench of the first trench type including a control electrode that is insulated from the semiconductor body. The semiconductor body further comprises: a barrier region and a drift volume having at least a first drift region wherein the barrier region couples the first drift region with the semiconductor channel region.

CROSS-REFERENCE TO RELATED APPLICATION

This Utility Patent Application is a continuation application of U.S.Ser. No. 15/647,885 filed Jul. 12, 2017 and claims priority to GermanPatent Application No. 10 2016 112 721.3, filed Jul. 12, 2016, which isincorporated herein by reference.

TECHNICAL FIELD

This specification refers to embodiments of a bipolar powersemiconductor device and to embodiments of a method of processing abipolar power semiconductor device. In particular, this specification isdirected to embodiments of an n-channel power semiconductor devicehaving a p-layer in the drift volume and to corresponding embodiments ofa power semiconductor device processing method.

BACKGROUND

Many functions of modern devices in automotive, consumer and industrialapplications, such as converting electrical energy and driving anelectric motor or an electric machine, rely on power semiconductordevices. For example, Insulated Gate Bipolar Transistors (IGBTs), MetalOxide Semiconductor Field Effect Transistors (MOSFETs) and diodes, toname a few, have been used for various applications including, but notlimited to switches in power supplies and power converters.

A power semiconductor device usually comprises a semiconductor bodyconfigured to conduct a load current along a load current path betweentwo load terminals of the device. Further, the load current path may becontrolled by means of an insulated control electrode, sometimesreferred to as gate electrode. For example, upon receiving acorresponding control signal from, e.g., a driver unit, the controlelectrode may set the power semiconductor device in one of a conductingstate, also referred to as on-state, and a blocking state, also referredto as off-state.

For a given application, a power semiconductor device may have to complywith some ratings regarding, e.g., a minimum voltage blocking capabilityand/or a minimum nominal load current capability, to a name a fewexamples. In an exemplary application, a power semiconductor device,e.g., having an IGBT configuration, may be coupled to a DC link, e.g., acapacitor, and may be used for a DC-DC and/or a DC-AC conversion. Then,a requirement regarding a minimum voltage blocking capability couldstate that a minimum blocking voltage of said power semiconductor devicehas to amount to at least twice of the maximum of the DC link voltage,in an example.

On the other side, a given application shall usually exhibit a highdegree of efficiency. To this end, beyond said ratings, it mayadditionally be desirable that the power semiconductor device usedwithin the application exhibits low losses, e.g., low on-state and/orlow switching losses. Said losses are usually proportional to theratings, e.g., the higher the voltage blocking capability of a device,the higher are usually also its on-state losses.

SUMMARY

According to an embodiment, a bipolar power semiconductor device (in thefollowing also referred to as “power semiconductor device”) having asemiconductor body configured to conduct a load current between itsfirst load terminal and its second load terminal comprises: a sourceregion of a first conductivity type and being electrically connected tothe first load terminal; a semiconductor channel region implemented inthe semiconductor body and having a second conductivity type andseparating the source region from a remaining portion of thesemiconductor body; a trench of a first trench type extending in thesemiconductor body along an extension direction and being arrangedadjacent to the semiconductor channel region, the trench of the firsttrench type including a control electrode that is insulated from thesemiconductor body by an insulator, wherein the control electrode isconfigured to control a path of the load current in the semiconductorchannel region; and at least one emitter region of the secondconductivity type that is implemented in the semiconductor body and thatis electrically connected to the second load terminal. The semiconductorbody further comprises: a barrier region the first conductivity type;and a drift volume having at least a first drift region of the secondconductivity type, wherein the barrier region couples the first driftregion with the semiconductor channel region. The semiconductor bodyalso comprises a buffer region of the first conductivity type that isarranged between the drift volume of the semiconductor body on one sideand the emitter region on the other side, wherein the first drift regionhas a total extension along the extension direction of at least 5% ofthe total extension of the semiconductor body along the extensiondirection.

According to a further embodiment, a bipolar power semiconductor device(in the following also referred to as “power semiconductor device”)having a semiconductor body configured to conduct a load current betweenits first load terminal and its second load terminal comprises: a sourceregion of a first conductivity type and being electrically connected tothe first load terminal; a semiconductor channel region implemented inthe semiconductor body and having a second conductivity type andseparating the source region from a remaining portion of thesemiconductor body; a control electrode that is insulated from thesemiconductor body by an insulator, wherein the control electrode isconfigured to control a path of the load current in the semiconductorchannel region; and at least one emitter region of the secondconductivity type that is implemented in the semiconductor body and thatis electrically connected to the second load terminal. The semiconductorbody further comprises: a drift volume having at least a first driftregion being coupled with the semiconductor channel region and havingthe second conductivity type; a buffer region of the first conductivitytype that is arranged between the drift volume of the semiconductor bodyon one side and the emitter region on the other side, wherein the firstdrift region has a total extension along an extension direction of atleast 5% of the total extension of the semiconductor body along theextension direction.

According to a yet further embodiment, a method of processing a bipolarpower semiconductor device (in the following also referred to as “powersemiconductor device”) having a semiconductor body comprises: creating asource region with a first conductivity type; creating a semiconductorchannel region in the semiconductor body with a second conductivity typesuch that the semiconductor channel region separates the source regionfrom a remaining portion of the semiconductor body; providing a controlelectrode for controlling a path of a load current in the semiconductorchannel region, and an insulator that insulates the control electrodefrom the semiconductor body; creating at least one emitter region of thesecond conductivity type in the semiconductor body; creating a driftvolume having at least a first drift region in the semiconductor bodywith the second conductivity type such that the first drift region iscoupled with the semiconductor channel region; and creating a bufferregion of the first conductivity type and being arranged between thedrift volume of the semiconductor body on one side and the emitterregion on the other side; wherein the first drift region has a totalextension along an extension direction of at least 5% of the totalextension of the semiconductor body along the extension direction.

Those skilled in the art will recognize additional features andadvantages upon reading the following detailed description, and uponviewing the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The parts in the figures are not necessarily to scale, instead emphasisbeing placed upon illustrating principles of the invention. Moreover, inthe figures, like reference numerals designate corresponding parts. Inthe drawings:

FIGS. 1A-D each schematically and exemplarily illustrate a section of avertical cross-section of a bipolar power semiconductor device inaccordance with some embodiments;

FIG. 2 schematically and exemplarily illustrates a section of a verticalcross-section of a bipolar power semiconductor device in accordance withone or more embodiments;

FIG. 3A-B each schematically and exemplarily illustrate a section of ahorizontal projection of a bipolar power semiconductor device inaccordance with one or more embodiments;

FIG. 3C schematically and exemplarily illustrates a section of avertical cross-section of a bipolar power semiconductor device inaccordance with one or more embodiments;

FIG. 4 schematically and exemplarily illustrates a section of a verticalcross-section of a bipolar power semiconductor device along with anexemplary illustration of courses of dopant concentrations in accordancewith one or more embodiments;

FIG. 5A schematically and exemplarily illustrates a course of a dopantconcentration in an extension direction in accordance with one or moreembodiments; and

FIG. 5B schematically and exemplarily illustrates a course of anelectric field strength in an extension direction in accordance with oneor more embodiments.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings which form a part hereof and in which are shown byway of illustration specific embodiments in which the invention may bepracticed.

In this regard, directional terminology, such as “top”, “bottom”,“below”, “front”, “behind”, “back”, “leading”, “trailing”, “above” etc.,may be used with reference to the orientation of the figures beingdescribed. Because parts of embodiments can be positioned in a number ofdifferent orientations, the directional terminology is used for purposesof illustration and is in no way limiting. It is to be understood thatother embodiments may be utilized and structural or logical changes maybe made without departing from the scope of the present invention. Thefollowing detailed description, therefore, is not to be taken in alimiting sense, and the scope of the present invention is defined by theappended claims.

Reference will now be made in detail to various embodiments, one or moreexamples of which are illustrated in the figures. Each example isprovided by way of explanation, and is not meant as a limitation of theinvention. For example, features illustrated or described as part of oneembodiment can be used on or in conjunction with other embodiments toyield yet a further embodiment. It is intended that the presentinvention includes such modifications and variations. The examples aredescribed using specific language which should not be construed aslimiting the scope of the appended claims. The drawings are not scaledand are for illustrative purposes only. For clarity, the same elementsor manufacturing steps have been designated by the same references inthe different drawings if not stated otherwise.

The term “horizontal” as used in this specification intends to describean orientation substantially parallel to a horizontal surface of asemiconductor substrate or of a semiconductor structure. This can be forinstance the surface of a semiconductor wafer or a die. For example,both the first lateral direction X and the second lateral direction Ymentioned below can be horizontal directions, wherein the first lateraldirection X and the second lateral direction Y may be perpendicular toeach other.

The term “vertical” as used in this specification intends to describe anorientation which is substantially arranged perpendicular to thehorizontal surface, i.e., parallel to the normal direction of thesurface of the semiconductor wafer. For example, the extension directionZ mentioned below may be an extension direction that is perpendicular toboth the first lateral direction X and the second lateral direction Y.

In this specification, n-doped is referred to as “first conductivitytype” while p-doped is referred to as “second conductivity type”.Alternatively, opposite doping relations can be employed so that thefirst conductivity type can be p-doped and the second conductivity typecan be n-doped.

Further, within this specification, the term “dopant concentration” mayrefer to an average dopant concentration or, respectively, to a meandopant concentration or to a sheet charge carrier concentration of aspecific semiconductor region or semiconductor zone. Thus, e.g., astatement saying that a specific semiconductor region exhibits a certaindopant concentration that is higher or lower as compared to a dopantconcentration of another semiconductor region may indicate that therespective mean dopant concentrations of the semiconductor regionsdiffer from each other.

In the context of the present specification, the terms “in ohmiccontact”, “in electric contact”, “in ohmic connection”, and“electrically connected” intend to describe that there is a low ohmicelectric connection or low ohmic current path between two regions,sections, zones, portions or parts of a semiconductor device or betweendifferent terminals of one or more devices or between a terminal or ametallization or an electrode and a portion or part of a semiconductordevice. Further, in the context of the present specification, the term“in contact” intends to describe that there is a direct physicalconnection between two elements of the respective semiconductor device;e.g., a transition between two elements being in contact with each othermay not include a further intermediate element or the like.

In addition, in the context of the present specification, the term“electric insulation” is used, if not stated otherwise, in the contextof its general valid understanding and thus intends to describe that twoor more components are positioned separately from each other and thatthere is no ohmic connection connecting those components. However,components being electrically insulated from each other may neverthelessbe coupled to each other, for example mechanically coupled and/orcapacitively coupled and/or inductively coupled. To give an example, twoelectrodes of a capacitor may be electrically insulated from each otherand, at the same time, mechanically and capacitively coupled to eachother, e.g., by means of an insulation, e.g., a dielectric.

The term “power semiconductor device” as used in this specificationintends to describe a semiconductor device on a single chip with highvoltage blocking and/or high current carrying capabilities. In otherwords, such power semiconductor device is configured for a high loadcurrent, typically in the Ampere range, e.g., up to several ten orhundred Ampere, and/or high voltages, typically above 5 V, or above 15 Vor more typically 400V and, e.g., up to some 1000 Volts.

For example, the term “power semiconductor device” as used in thisspecification is not directed to logic semiconductor devices that areused for, e.g., storing data, computing data and/or other types ofsemiconductor based data processing.

Specific embodiments described in this specification thus pertain to,without being limited thereto, a bipolar power semiconductor device (inthe following simply also referred to as “semiconductor device” or“device”) that may be used within a power converter or a power supply,e.g., for converting a first power signal into a second power signaldifferent from the first power signal. For example, to this end, thebipolar power semiconductor device may comprise one or more powersemiconductor cells, such as a monolithically integrated transistorcell, a monolithically integrated diode cell, and/or a monolithicallyintegrated IGBT cell, and/or a monolithically integrated RC-IGBT cell,and/or a monolithically integrated MOS Gated Diode (MGD) cell, and/orderivatives thereof. Such diode cells and/or such transistor cells maybe integrated in a semiconductor chip, wherein a number of such chipsmay be integrated in a power semiconductor module, such as an IGBTmodule.

FIG. 3A schematically and exemplarily illustrates a section of ahorizontal projection of a bipolar power semiconductor device 1 inaccordance with one or more embodiments. In the following, each of theterms “power semiconductor device” and “semiconductor device” refer to abipolar power semiconductor device. Also FIG. 3B schematically andexemplarily illustrates a section of a horizontal projection of a powersemiconductor device 1 in accordance with one or more other embodiments.In both of FIG. 3A and FIG. 3B, the horizontal projection may be inparallel to the plane defined by the first lateral direction X and thesecond lateral direction Y. The components of the semiconductor device 1may each extend along the extension direction Z that may beperpendicular to each of the first lateral direction X and the secondlateral direction Y.

The semiconductor device 1 may comprise an active cell field 16 thatincludes one or more active cells, e.g., MOS (Metal Oxide Semiconductor)cells, in the following simply referred to as “cells”, wherein each ofsaid cells may comprise at least one control electrode 131. The numberof cells may be within the range of 100 to 100000, for example. Theactive cell field 16 may be configured to conduct a total load current,wherein the total load current may be greater than 1 A, greater than 10A or even greater than 100 A. In the following, said total toad currentis also simply referred to as load current.

The active cell field 16 may be surrounded by an edge termination zone18 of the semiconductor device 1. For example, the edge termination zone18 does not include any active cells. The edge termination zone 18 maybe terminated by an edge 19, which may have come into being, e.g., bydicing a chip out of a wafer.

Further, the active cell field 16 or, respectively, the active cellfield 16 and the edge termination zone 18 may be configured to block ablocking voltage of at least 20 V, of at least 100 V, of at least 400 Vor of at least 1000 V.

As schematically illustrated in FIG. 3A, the cells, e.g., their controlelectrodes 131, may exhibit a stripe configuration. Accordingly, each ofthe cells and the components they may comprise, e.g., the controlelectrodes 131, may extend along substantially the entire active cellfield 16 along one of the first lateral direction X and the secondlateral direction Y (as illustrated), e.g., bordering a transitionregion between the active cell field 16 and the edge termination zone18. For example, the total lateral extension of a respective (stripe)cell amounts to less than 30%, less than 5%, or even less than 1% of thetotal extension of the active cell field 16 along one of the firstlateral direction X and the second lateral direction Y.

In another embodiment that is schematically illustrated in FIG. 3B, thecells may exhibit a needle configuration (also referred to as cellularconfiguration) whose total lateral extensions along each of the firstlateral direction X and the second lateral direction Y amount to only afraction of the total lateral extensions along the first lateraldirection X and the second lateral direction Y of the active cell field16. For example, the total lateral extension of a respective needle cellamounts to less than 30%, less than 5%, or even less than 1% of thetotal extension of the active cell field 16 along one of the firstlateral direction X and the second lateral direction Y.

In another embodiment, the active cell field 16 may comprise both typesof cells, e.g., one or more cells in a stripe configuration and one ormore cells in a needle configuration.

Both the active cell field 16 and the edge termination zone 18 may atleast partially be formed within a joint semiconductor body 10 of thedevice 1. The semiconductor body 10 may be configured to carry the totalload current that may be controlled, e.g., by means of the controlelectrodes 131. For example, the control electrodes 131 can beimplemented as trench electrodes or a planar electrodes, as will beexplained in more detail below with respect to FIGS. 1A-D and FIG. 2.

As has been explained above, the semiconductor device 1 described hereincan be a bipolar power semiconductor device 1. Thus, the total loadcurrent within the semiconductor body 10 may be constituted by a firstload current formed by first charge carriers of a first conductivitytype and by a second load current formed by second charge carriers of asecond conductivity type complimentary to the first conductivity type.For example, the first charge carriers are electrons and the secondcharge carriers are holes.

Regarding now each of FIGS. 1A-D, which each schematically andexemplarily illustrate a section of a vertical cross-section of thesemiconductor device 1 in accordance with some embodiments, thesemiconductor device 1 may comprise a first load terminal 11 and asecond load terminal 12. For example, the first load terminal 11 isarranged separately from the second load terminal 12. The semiconductorbody 10 may be coupled to each of the first load terminal 11 and thesecond load terminal 12 and may be configured to receive said loadcurrent via the first load terminal structure 11 and to output the loadcurrent via the second load terminal 12 and/or vice versa.

The semiconductor device 1 may exhibit a vertical set-up, according towhich, for example, the first load terminal structure 11 is arranged ona frontside of the semiconductor device 1 and the second load terminalstructure 12 is arranged on a backside of the semiconductor device 1. Inanother embodiment, the semiconductor device 1 may exhibit a lateralset-up, according to which, e.g., each of the first load terminalstructure 11 and the second load terminal structure 12 are arranged onthe same side of the semiconductor device 1.

For example, the first load terminal 11 comprises a first metallization,e.g., a frontside metallization, and the second load terminal 12 maycomprise a second metallization, e.g., a backside metallization.Further, one or both of the first load terminal 11 and the second loadterminal 12 may comprise a diffusion barrier.

Within the present specification, the direction of the total loadcurrent is expressed in the conventional manner, i.e., as a flowdirection of positive charge carriers such as holes and/or as directionopposite to a flow of negative charge carriers such as electrons. Aforward direction of the total load current may point, for example, fromthe second load terminal 12 to the first load terminal 11.

For controlling the load current, the semiconductor device 1 may furthercomprise said control electrode(s) 131. For example, the semiconductordevice 1 may be configured to be set into one of the blocking state andthe conducting state by means of said control electrode(s) 131. Forexample, said control electrodes 131 may be configured as planar controlelectrodes 131 or as trench control electrodes 131.

In an embodiment, for setting the semiconductor device 1 into aconducting state during which the load current in the forward directionmay be conducted, the control electrode 131 may be provided with acontrol signal having a voltage within a first range. For setting thesemiconductor device 1 into a blocking state during which a forwardvoltage may be blocked and flow of the load current in the forwarddirection is avoided, the control electrode 131 may be provided with thecontrol signal having a voltage within a second range different from thefirst range.

In an embodiment, the control signal may be provided by applying avoltage between the control electrode 131 and the first load terminal 11and/or by applying a voltage between the control terminal 13 and thesecond load terminal 12.

The power semiconductor device 1 may include a source region 101electrically connected to the first load terminal 11. The source region101 may be a semiconductor source region and, e.g., implemented in thesemiconductor body 10. For example, the source region 101 has the firstconductivity type, e.g., it comprises dopants of the first conductivitytype, e.g., at a dopant concentration in the range of 10¹⁹ cm⁻³ to 10²²cm⁻³, e.g., 5*10¹⁹ cm⁻³ to 1*10²¹ cm⁻³.

The power semiconductor device 1 may further include a semiconductorchannel region 102 that is implemented in the semiconductor body 10 andthat may have the second conductivity type, e.g., it comprises dopantsof the second conductivity type. The semiconductor channel region 102,in the following also referred to as channel region 102, may separatethe source region 101 from a remaining portion of the semiconductor body10, e.g., the semiconductor channel region 102 may isolate the sourceregion 101 from at least one of the regions 103 and 104 presented below.It shall be understood that the channel region 102 may also beelectrically connected to the first load terminal 11. For example,referring to the embodiment schematically illustrated in FIG. 2, anumber of plugs 111 may be provided that may be configured to ensure theelectrical connection between the first load terminal 11 on the one sideand each of the source region 101 and the channel region 102 on theother side.

A transition between the source region 101 and the semiconductor channelregion 102 may form a first junction 1012, e.g., a first pn-junction.

As indicated above, for controlling the load current in thesemiconductor body 10, the semiconductor device 1 may comprise one ormore control electrodes 131, which may be implemented as a trenchelectrode, as schematically illustrated in FIGS. 1A-B and in FIG. 2, oras a planar electrode, as schematically illustrated in FIGS. 1C-D. Atthis point, it shall already be emphasized that the embodiments inaccordance with FIGS. 1A-B may also be provided with planar controlelectrodes 131 instead of trench control electrodes 131, and that theembodiments in accordance with FIGS. 1C-D may also be provided withtrench control electrodes 131 instead of planar control electrodes 131.

Irrespective of its configuration (planar electrode or trenchelectrode), the control electrode 131 may be electrically insulated fromeach of the first load terminal 11 and the semiconductor body 10. Tothis end, the semiconductor device 1 may comprise an insulator 132 thatinsulates the control electrode 131. If the power semiconductor device 1exhibits a trench architecture, as schematically illustrated in FIGS.1A-B and in FIG. 2, the control electrode 131 and the insulator 132 maybe included in a trench 13 of a first trench type. The trench 13 mayexhibit a cellular configuration or stripe configuration (cf. FIGS.3A-B).

For example, the control electrode 131 may be configured to control apath of the load current in the semiconductor channel region, e.g., byinducing an inversion channel in the channel region 102 so as to ensureflow of the load current and/or by breaking up the inversion channel soas to initiate the blocking state.

The semiconductor device 1 may further comprise a drift volume formed byat least a first drift region 104 that is implemented in thesemiconductor body 10. In accordance with an embodiment, the first driftregion 104 has the second conductivity type, e.g., it comprises dopantsof the second conductivity type, e.g., of the same conductivity type asthe dopants in the channel region 102. For example, the first driftregion 104 is a weakly doped p-region. The first drift region 104 may bean electrically floating region; e.g., the first drift region 104 is notelectrically connected, e.g., not in contact with the first loadterminal 11, whereas, as indicated above, each of the source region 101and the channel region 102 may be in contact with the first loadterminal 11.

Thus, it shall be understood that, in accordance with an embodiment, thefirst drift region 104 can be doped with dopants of the sameconductivity type as the dopants included in the channel region 102.Accordingly, an n-channel may be induced in a p-doped channel region 102and, at the same time, the first drift region 104 that may be coupled tosaid p-doped channel region 102 (either directly or via a barrierregion, as explained in more detail below) can be a p-drift region 104,in accordance with one or more embodiments.

The first drift region 104 may be coupled to the channel region 102. Inaccordance with an embodiment, e.g., as schematically and exemplarilyillustrated in FIGS. 1C-D, the first drift region 104 may be in contactwith the channel region 102. As emphasized above, the embodimentsillustrated in FIGS. 1C-D may also be provided with trench controlelectrodes 131 instead of planar control electrodes 131. Accordingly,said embodiments may each include the trench 13 of the first trench typethat each extends into the semiconductor body 10 along the extensiondirection Z and that is arranged adjacent to the semiconductor channelregion 102, wherein the trench 13 may include the control electrode 131and at least a part of the insulator 132, e.g., in a manner asillustrated in FIGS. 1A-B.

In accordance with another embodiment, e.g., as schematically andexemplarily illustrated in FIGS. 1A-B and in FIG. 2, the powersemiconductor device 1 may optionally comprise a barrier region 103 thathas the first conductivity type, e.g., it comprises dopants of the firstconductivity type. For example, the barrier region 103 is an n-dopedregion. In an embodiment, this barrier region 103 may be electricallyfloating, e.g., the barrier region 103 is not electrically connected tothe first load terminal 11. A transition between the barrier region 103and the channel region 102 may form a second junction 1023, e.g., asecond pn-junction. In an embodiment, the barrier region 103 may beconfigured to compensate or, respectively, to overcompensate an eventualreduction of a carrier confinement that may have been caused byincluding the first drift region 104 in the semiconductor body 10, e.g.,around trench bottoms. In another embodiment, the barrier region 103illustrated in FIG. 1A or in FIG. 1B is not provided, and the channelregion 102 is arranged in contact with the first drift region 104.

If the barrier region 103 is provided, a transition between the barrierregion 103 and the first drift region 104 may form a third junction1034, for example a third pn-junction.

Regarding now an exemplary configuration of the semiconductor body 10 inproximity to the second load terminal 12, the semiconductor device 1 maycomprise an emitter region 108 electrically connected to the second loadterminal 12. An embodiment of such emitter region 108 is schematicallyillustrated in each of FIGS. 1A-B. For example, the emitter region 108has the second conductivity type, e.g., it comprises dopants of thesecond conductivity type. The emitter region 108 can be a p⁺-emitterregion. In an embodiment, the emitter region 108 may also compriseemitter subregions (not illustrated) having dopants of the firstconductivity type, e.g., n⁺-emitter subregions, which may also bereferred to as “n-shorts”.

In an embodiment, the semiconductor device 1 may further comprise abuffer region 107 having the first conductivity type (e.g., it maycomprise dopants of the first conductivity type) and being arranged incontact with said drift volume of the semiconductor body 10, said driftvolume being at least partially formed by the first drift region 104, ashas been explained above. For example, the buffer region 107 is n⁺-dopedregion or an n⁺⁺-doped region. The buffer region 107 may also bereferred to as field stop region. For example, the buffer region 107 maybe arranged in contact with the emitter region 108 on the one side andmay be coupled to said drift volume on the other side.

In an embodiment, e.g., as schematically illustrated in FIG. 1A, thebuffer region 107 is arranged in contact with the first drift region104, wherein a transition between the first drift region 104 comprisingthe dopants of the second conductivity type and the buffer region 107comprising the dopants of first conductivity type may form a yet furtherjunction 1047, e.g., a further pn-junction.

In another embodiment, e.g., as schematically illustrated in FIG. 1B,the drift volume may additionally be formed by a second drift region105, wherein said second drift region 105 may have the firstconductivity type, e.g., it may comprise dopants of the firstconductivity type. For example, the first drift region 104 is a p⁻-driftregion and the second drift region 105 is an n⁻-drift region. Forexample, the second drift region 105 extends further along the extensiondirection Z than the first drift region 104, e.g., the second driftregion 105 may be arranged below the first drift region 104, e.g., in asandwich like manner. For example, if present, the buffer region 107 maythen be arranged in contact with the second drift region 105, wherein atransition 1057 between the second drift region 105 having the firstconductivity type and the buffer region 107 also having the firstconductivity type may thus form no junction, for example.

In an embodiment, the buffer region 107 exhibits a total extension DZ7along the extension direction Z and its dopant concentration mayincrease for at least 20% of said total extension. The increase mayoccur along even more than 50%, e.g., for at least 70% of said totalextension, for at least 90% of said total extension or for even morethan 95% of said total extension.

Further, the first drift region 104, which may be arranged in contactwith the buffer region 107 in an embodiment (cf. FIG. 1A), can exhibit atotal extension along the extension direction Z and its dopantconcentration may decrease for at least 50% of said total extension.Said decrease may occur along even more than 70%, e.g., for at least 80%of said total extension, for at least 90% of said total extension or foreven more than 95% of said total extension. Accordingly, in anembodiment of the power semiconductor 1, the first drift region 104 isarranged in contact with the buffer region 107, wherein in proximity tosaid contact, e. g., in proximity to the further junction 1047, thedopant concentration of the first drift region 104 may decrease whenapproaching the further junction 1047 and the dopant concentration ofthe buffer region 107 may increase when departing from the furtherjunction 1047.

Further exemplary dopant concentration profiles will be disclosed withrespect to FIG. 4.

With respect to the embodiments in accordance with FIG. 1C or FIG. 1D,it shall be understood that the region of the semiconductor body 10 inproximity to the second load terminal 12 may be configured in a mannersimilar or identical to the embodiments illustrated in FIG. 1A or 1B.Accordingly, the semiconductor body 10 of the embodiment in accordancewith FIG. 1C or of the embodiment in accordance with FIG. 1D maycomprise at least one of the emitter region 108 arranged in contact withthe second load terminal 12, and the buffer region 107, wherein saidregions 107 and 108 may be configured in a manner as exemplarilydescribed above.

Thus, it shall be understood that in accordance with every embodimentillustrated in FIGS. 1A to 5B, the power semiconductor device 1 mayexhibit a power transistor configuration, e.g., an IGBT configuration oran RC-IGBT configuration, wherein the first drift region 104 may havethe same conductivity type as the channel region 102, and wherein thefirst drift region 104 may be coupled to the channel region 102, e.g.,in a direct manner such that the first drift region 104 is arranged incontact with the channel region 102, or in an indirect manner, namely bymeans of said barrier region 103, and wherein the control electrode 131may be configured as a trench control electrode or as a planar controlelectrode.

Referring now to the embodiment is schematically illustrated in FIG. 1D,the drift volume may include one or more subregions 1041, wherein eachof the one or more subregions 1041 contributes to less than 10% or toless than 5% of the total volume of the drift volume, e.g. of the volumeof the first drift region 104. Further each of the one or moresubregions 1041 may have either the first or the second conductivitytype at a dopant concentration being greater by a factor of at least 100than the dopant concentration of the first drift region 104. Forexample, the subregions 1041 are formed by one or more p⁺-subregionsand/or by one or more n⁺-subregions. These one or more subregions 1041may allow for increasing the short circuit robustness. For example, theconcept of introducing highly doped subregions within a drift volume forincreasing a short circuit robustness is also described in DE 10 2015107 103 A1, the content of which is incorporated herein in its entirety.Thus, it shall be understood that, presently, the inventors haverecognized that the measures for increasing the short circuit robustnessas described in DE 10 2015 107 103 A1 may also be applied to thesemiconductor device 1 in accordance with embodiments described herein.E.g., the one or more subregions 1041 may also be included in the driftvolume comprising the first drift region 104 that may be doped withdopants of the same conductivity type as they are present in the channelregion 102. As indicated in FIG. 1D, said one or more subregions 1041may be arranged within the first drift region 104 of the drift volume,e.g., in a portion in proximity to the second load terminal 12, e.g., inproximity to a transition from the first drift region 104 to one of abuffer region and an emitter region (not illustrated in FIG. 1D; cf.regions 107 and 108 in other drawings, e.g., FIG. 1A). Further, if thedrift volume of the semiconductor device 1 of FIG. 1D is additionallyformed by the second drift region 105 (cf. e.g. FIG. 1B; not illustratedin FIG. 1D), said one or more subregions 1041 may additionally oralternatively be arranged within the second drift region 105, e.g., in amanner as described in DE 10 2015 107 103 A1.

Optional aspects of the embodiments according to FIGS. 1A-B and FIG. 2,where the control electrodes 131 may be included in a respective trench13 of the first trench type, shall now be disclosed. For example, thetrenches 13 of the first trench type extend in the semiconductor body 10along the extension direction Z. They may each be arranged adjacent to arespective semiconductor channel region 102, e.g., so as to be able tocontrol a path of the load current therein. The trenches 13 of the firsttrench type may each extend further along the extension direction Z intothe semiconductor body 10 than each of the first junction 1012 and, ifpresent, the second junction 1023, and also further than the thirdjunction 1034, in accordance with an embodiment. For example, thecontrol electrode 131 included in the trench 13 of the first trench typemay extend further along the extension direction Z than each of thefirst junction 1012 and, if present, i.e., if the optional barrierregion 103 is provided, the second junction 1023, and also further thanthe third junction 1034, in accordance with an embodiment. In anotherembodiment (not illustrated), the third junction 1034 is arranged deeperthan the bottom of the trench 13. Again, it shall be understood that thebarrier region 103 must not necessarily be provided. If the barrierregion 103 is not provided, the first drift region 104 may be arrangedin contact with the channel region 102 and, accordingly, in this casethe second junction 1023 and the third junction 1034 are notestablished, as has been elucidated above.

Further, the trenches 13 of the first trench type may each exhibit atotal extension DZT, measured from a surface 10-1 of the semiconductorbody 10, along the extension direction Z, wherein the third junction1034 formed by the transition between the barrier region 103 and thefirst drift region 104 is arranged within a level in the range of 50% to95% of said total extension DZT. Further, transition along the extensiondirection from the first drift region 104 to a remaining portion of thesemiconductor body 10, e.g., the transition 1047 or the transition 1045,can be arranged within a level greater than 200% of said total extensionDZT. Thus, the transition 1047 or the transition 1045 may be arrangedsignificantly below the bottoms of the trenches 13.

The first drift region 104 can be arranged in contact with at least arespective lower section of the trenches 13, the respective lowersection amounting to at least 10% of said total extension DZT. In otherwords, said lower trench sections may be embedded within the first driftregion 104 that may comprise the dopants of the second conductivitytype.

As illustrated, the semiconductor device 1 may comprise a plurality oftrenches 13 of said first trench type, wherein said trenches 13 can beare arranged along the first lateral direction X, forming, e.g., a micropattern trench (MPT) structure. Further, referring to the embodimentschematically illustrated in FIG. 2, the power semiconductor device 1may comprise a plurality of trenches 17 of a second trench type arrangedalong a first lateral direction X, wherein each trench 17 of the secondtype extends in the semiconductor body 10 along the extension directionZ, and wherein each trench 17 of the second trench type may include atrench electrode 171 that is insulated from the semiconductor body 10 bya trench insulator 172. Whereas the control electrodes 131 included inthe trenches 13 of the first trench type may be electrically connectedto each other, the trench electrodes 171 included in the trenches 17 ofthe second trench type can be electrically insulated from the controlelectrodes 131, in accordance with an embodiment. Nevertheless, thetrench electrodes 171 may exhibit equal spatial dimensions as comparedto the control electrodes 131 and may also be made of the same materialas the control electrodes 131. For example, the trench electrodes 171are implemented as so-called field plates and may be electricallyconnected to a fixed electrical potential, e.g., to the first loadterminal 11. In an embodiment, a trench 13 of the first trench type isarranged adjacent to two trenches 17 of the second trench type, and atrench 17 of the second trench type is arranged adjacent to two trenches13 of the first trench type, as schematically illustrated in FIG. 2.

Each of the trenches 13 of the first trench type and each of thetrenches 17 of the second trench type may traverse each of thesemiconductor channel region 102, the barrier region 103 (if present)and may further extends into the first drift region 104. For example,adjacent trenches—which may either be two trenches 13 of the firsttrench type, two trenches 17 of the second trench type, or one firsttrench type trench 13 and one second trench type trench 17—may beseparated from each other by a respective mesa zone 14 along the firstlateral direction X. Each mesa zone 14 may exhibit a width WM within therange of 10 nm to 10 μm, for example. Further, each mesa zone 14 maycomprises a section of each of the source region 101, the semiconductorchannel region 102, the barrier region 103 (if present) and the firstdrift region 104. Accordingly, in an embodiment, the first drift region104 may extend into the mesa zones 14. As illustrated in each of FIGS.1A-B and FIG. 2, the barrier region 103 may entirely be arranged withthe mesa zones 14.

Even though each of FIGS. 1A-B and FIG. 2 illustrate the barrier region103 within the mesa zones 104, it shall be understood that this barrierregion 103 must not necessarily be present in the illustratedembodiments. For example, if the barrier region 103 is absent, the firstdrift region 104 may extend further against the extension direction Zand may be arranged in contact with the channel regions 102, as it isthe case in accordance with the embodiment schematically illustrated inFIGS. 1C-D. Then, what has been stated above with regards to the totalextension of the trenches 13 of the first trench type may also applywith respect to a transition between the channel region 102 and thefirst drift region 104 (cf. e.g., transition 1024 indicated in FIGS.1C-D). Accordingly, the trenches 13 of the first trench type may theneach extend further along the extension direction Z into thesemiconductor body 10 than said transition 1024, in accordance with anembodiment. For example, the control electrode 131 included in thetrench 13 of the first trench type may also extend further along theextension direction Z than said transition 1024, in accordance with anembodiment. Further, regarding the embodiments in accordance with FIG.1C or FIG. 1D, it shall be understood that these embodiments may alsoinclude at least one of said second drift region 105, a buffer region107 and an emitter region 108.

As has already been explained with respect to FIGS. 3A-B, the powersemiconductor device 1 may comprise an active cell field 16 and an edgetermination zone 18 surrounding the active cell field 16. For example,the first drift region 104 having the second conductivity type isexclusively arranged in the active cell field 16. There are a number ofpossibilities how to ensure that the first drift region 104 extends onlywithin the active cell field 16, one of which is schematically andexemplarily illustrated in FIG. 3C. In the embodiment illustrated inFIG. 3C, the drift volume of the semiconductor device 1 may beconstituted by the first drift region 104 and the second drift region105.

Regarding the active cell field 16, on the one side facing to the secondload terminal 12, the first drift region 104 may thus be arranged incontact with the second drift region 105, which may be positioned belowwith the first drift region 104. On the other side facing to the firstload terminal 11, the first drift region 104 may be coupled to portionsof the semiconductor body 10 that may be electrically connected to thefirst load terminal 11 and that may be controlled by the controlelectrodes 131, e.g., the first drift region 104 may be coupled to thechannel region 102, e.g. directly or, if present, by means of thebarrier region 103 (not illustrated in FIG. 3C).

A transition from the active cell field 16 to the edge termination zone18 may comprise a deep trench 15 that extends from the surface 10-1along the extension direction Z and that may entirely traverse the firstdrift region 104. For example, if the first drift region 104 isimplemented as a first drift layer 104, the deep trench 15 may interruptthis layer 104 such that a boarder layer portion 1042 within the edgetermination zone 18 is separated from the remaining part of the firstdrift region 104 and is not contact anymore to said portions of thesemiconductor body 10 that may be may be electrically connected to thefirst load terminal 11 and that may be controlled by the controlelectrodes 131. If the semiconductor device 1 further comprises thesecond drift region 105, as schematically illustrated in FIG. 3C, thedeep trench 15 may also entirely traverse the second drift region 105such that a boarder region portion 1052 in the edge termination zone 18is separated from the remaining part of the second drift region 105.Further, within the edge termination zone 18, there may be included oneor more guard rings 181, as they are known to the skilled person. Inanother embodiment, the one or more guard rings 181 are not provided inthe edge termination zone 18 that is separated from the active cellfield 16 by means of the deep trench 15. Further, the if the edgetermination zone 18 is separated from the active cell field 16 by meansof the deep trench 15, the edge termination zone 18 may be formed by asubstantially unstructured semiconductor region, comprising, e.g.,dopants of the first conductivity type.

For example, referring again to FIGS. 3A-B, the cells of the active cellfield 16 that are arranged closest to the edge termination zone 18 maybe configured in a manner as illustrated in one of FIGS. 1A-2, butwithout the source region 101. E.g., the cells of the active cell field16 that are arranged closest to the edge termination zone 18 may beconfigured similar to the remaining cells of the active cell field 16,but with the difference that these cell do not exhibit the source region101. Rather, a source region for these “boundary” cells is not providedand these cells, even though belonging to the active cell field 16, donot conduct any load current, in accordance with an embodiment.

In accordance with a further embodiment, also a method of processing apower semiconductor device 1 having a semiconductor body 10 ispresented. For example, the method comprises creating a source region101 with a first conductivity type, e.g., by carrying out at least oneof an epitaxy processing step, a diffusion processing step, and animplantation step. Further, the method may comprise creating asemiconductor channel region 102 in the semiconductor body 10 with asecond conductivity type, e.g., by carrying out at least one of anepitaxy processing step, a diffusion processing step, and animplantation step, such that the semiconductor channel region 102separates the source region 101 from a remaining portion of thesemiconductor body 10. Further, the method may include providing acontrol electrode 131 for controlling a path of a load current in thesemiconductor channel region 102, and an insulator 132 that insulatesthe control electrode 131 from the semiconductor body 10. The method mayfurther include: creating at least one emitter region 108 of the secondconductivity type in the semiconductor body 10; and creating a driftvolume having at least a first drift region 104 in the semiconductorbody 10 with the second conductivity type, e.g., by carrying out atleast one of an epitaxy processing step, a diffusion processing step,and an implantation step such that the first drift region 104 is coupledwith the semiconductor channel region 102; and creating a buffer region107 of the first conductivity type and being arranged between the driftvolume of the semiconductor body 10 on one side and the emitter region108 on the other side. Creating the first drift region 104 may occurprior to creating the source region 101, the channel region 102 and alsoprior to creating the control electrode 131. What has been stated aboveregarding the embodiments of the power semiconductor device 1, e.g., itscomponents 10, 11, 12, 101, 102, 103, 104, 105, 107, 108 may analogouslyapply to the embodiment of the method of processing a powersemiconductor device.

FIG. 4 schematically and exemplarily illustrates a section of a verticalcross-section of the power semiconductor device 1 along with anexemplary illustration of courses of dopant concentrations CC in theextension direction Z accordance with one or more embodiments. Forexample, the source region 101, which may begin at the surface 10-1 ofthe semiconductor body 10, may exhibit a total extension DZ1 in theextension direction Z within the range of 0.05 μm to 2 μm, or within therange of 0.1 μm to 0.5 μm. For example, the concentration of the dopantsof the first conductivity type is substantially constant along saidtotal extension DZ1, e.g., the dopant concentration is within the rangeof 1e18 cm⁻³ to 1e21 cm⁻³, or within the range of 1e19 cm⁻³ to 5e20cm⁻³. As already indicated, below the source region 101, there may bearranged the channel region 102.

For example, the channel region 102 may exhibit a total extension DZ2 inthe extension direction Z within the range of 0.5 μm to 5 μm, or withinthe range of 1.0 μm to 3.5 μm. For example, the concentration of thedopants of the second conductivity varies along said total extensionDZ2, e.g., the dopant concentration is within the range of 1e16 cm⁻³ to1e18 cm⁻³, or within the range of 1e17 cm⁻³ to 5e17 cm⁻³, and exhibits,for example, a peak in a central part of the channel region 102.

As further been explained above, the first drift region 104 having thedopants of the second conductivity type may be arranged below thechannel region 102 and may be coupled thereto, for example directly,i.e., in contact to the channel region 102, or by means of the barrierregion 103, which is not illustrated in FIG. 3 and which must notnecessarily be present in the semiconductor body 10. For example, thefirst drift region 104 may exhibit a total extension DZ4 in theextension direction Z within the range of 5 μm to 200 μm, or within therange of 5% to 50% of the total thickness of the semiconductor body 10in the extension direction Z, or within the range of 20 μm to 100 μm.The thickness DZ4 may depend on a desired voltage rating of thesemiconductor device 1. Further, with regards to the method ofprocessing a bipolar power semiconductor device described above, itshall be understood that providing the first drift region 104 with thethickness DZ4 (amounting, e.g., to at least 5% of the thickness of thesemiconductor body 10) can include a step of back thinning and/orpolishing a substrate; e.g., said thickness DZ4 may be provided afterthe entire processing of the bipolar power semiconductor device has beenfinished. For example, the concentration of the dopants of the secondconductivity varies along said total extension DZ4, e.g., the dopantconcentration is within the range of 2e12 cm⁻³ to 2e15 cm⁻³, or withinthe range of 5e12 cm⁻³ to 3e14 cm⁻³, or within the range 1*10¹³ cm⁻³ to2*10¹⁵ cm⁻³, and the dopant concentration may decrease along theextension direction Z, as schematically illustrated in FIG. 4, e.g. forat least 50% of said total extension DZ4. Said decrease may occur alongeven more than 70%, e.g., for at least 80% of said total extension DZ4,for at least 90% of said total extension DZ4 or for even more than 95%of said total extension DZ4. For example, the decrease in dopantconcentration amounts to a factor of at least 2, starting from a valuepresent in an upper half of said total extension DZ4. In anotherembodiment, the dopant concentration of the first drift region 104 maybe substantially constant along the total extension DZ4.

As indicated above, the semiconductor body 10 may further comprise asecond drift region 105, wherein it shall be understood that this seconddrift region 105 must not necessarily be present. Thus, in contrast tothe schematic illustration in FIG. 4, along the extension direction Z,the first drift region 104 may directly contact the buffer region 107,in accordance with an embodiment, e.g., by the first drift region 104extending further along the extension direction Z and by the bufferregion 107 extending further against the extension direction Z. Ifpresent, the second drift region 105 may exhibit a total extension DZ5in the extension direction Z within the range of 10 μm to 650 μm, orwithin the range of 40 μm to 200 μm, or within the range of 15% to 80%of the total thickness of the semiconductor body 10 in the extensiondirection Z. Also, thickness DZ5 may depend on a desired voltage ratingof the semiconductor device 1. For example, the concentration of thedopants of the first conductivity type is substantially constant alongsaid total extension DZ5, e.g., the dopant concentration is within therange of 2e12 cm⁻³ to 4e14 cm⁻³, or within the range of 5e12 cm⁻³, to9e13 cm⁻³. For example, said dopant concentration is determined independence on a desired voltage rating of the semiconductor device 1.

Regarding now the buffer region 107, which may be, as indicated above,arranged directly in contact with the first drift region 104, the bufferregion 107 may exhibit a total extension DZ7 in the extension directionZ within the range of 1 μm to 50 μm, or within the range of 5 μm to 30μm. Also, thickness DZ7 may depend on a desired voltage rating of thesemiconductor device 1. For example, the concentration of the dopants ofthe first conductivity varies along said total extension DZ7; themaximum dopant concentration can be within the range of 1e14 cm⁻³ to5e18 cm⁻³, or within the range of 2e14 cm⁻³ to 5e16 cm⁻³, and the dopantconcentration may increase along the extension direction Z, asschematically illustrated in FIG. 4, e.g. for at least 30%, for at least50% or for at least 70% of said total extension DZ7. Said increase mayoccur along even more than 70%, e.g., for at least 80% of said totalextension DZ7, for at least 90% of said total extension DZ7 or for evenmore than 95% of said total extension DZ7. For example, the increase indopant concentration amounts to a factor of at least 2, starting from avalue present in an upper half of said total extension DZ7.

Further, the semiconductor body 10 may include the emitter region 108,which may be in contact with the second load terminal 12 and which maycomprise dopants of the second conductivity type. For example, theemitter region 108 may exhibit a total extension DZ8 in the extensiondirection Z within the range of 0.02 μm to 15 μm, or within the range of0.2 μm to 1 μm. For example, the concentration of the dopants of thefirst conductivity type is substantially constant along said totalextension DZ8 or said concentration may follow a Gaussian-like course,e.g., the dopant concentration is within the range of 5e16 cm⁻³ to 1e21cm⁻³, or within the range of 1e17 cm⁻³ to 1e18 cm⁻³.

FIG. 5A schematically and exemplarily illustrates a course of a dopantconcentration CC of an embodiment of the first drift region 104 in theextension direction Z in accordance with one or more embodiments. Forexample, the first drift region 104 may exhibit a total extension DZ4 inthe extension direction Z amounting to approximately 40 μm. For example,the concentration of the dopants of the second conductivity decreasesalong substantially the entire total extension DZ4, e.g., a start valueCC41 within the range of 1e13 cm⁻³ to 2e15 cm⁻³ down to an end valueCC42 within the range of 2e12 cm⁻³ to 2e13 cm⁻³. For example, the startvalue CC41 may be present in proximity to the transition between thechannel region 102 and the first drift region 104 (cf. e.g., transition1024 indicated in FIGS. 1C-D), and the end value CC42 may be present inproximity to a transition between the first drift region 104 and thebuffer region 107 (cf. e.g., transition 1047 indicated in FIGS. 1A-B).As the first drift region 104 may be terminated, along the extensiondirection Z, by a semiconductor region that has dopants of the firstconductivity type, i.e., terminated by a junction, said end value CC42may be substantially lower, e.g. close to zero. The decrease may occuralong even more than 70%, e.g., for at least 80% of said total extensionDZ4, for at least 90% of said total extension DZ4 or for even more than95% of said total extension DZ4. For example, the decrease may exhibit asubstantially linear course or, in another embodiment, an exponentialcourse. Instead of decreasing, the dopant concentration may also beconstant or increase along the extension direction Z. Alternatively oradditionally, the dopant concentration in the first drift region 104 mayalso exhibit one or more maxima or minima along the extension directionZ or may exhibit graded or stepped profile, or a turtle shell profile,in accordance with one or more other embodiments.

As indicated above, the power semiconductor device 1 may be operable ina blocking state and in a conducting state. FIG. 5B schematically andexemplarily illustrates a course of an electric field strength E in theextension direction Z during the blocking state in accordance with oneor more embodiments. Thus, a voltage may be applied between the loadterminals 12 and 11 and flow of a load current is prevented, e.g., bymeans of providing a corresponding control signal to the controlelectrodes 131 such that inducement of an inversion channel in thechannel region 102 is prevented. Further, the semiconductor body 10 mayexhibit a total extension in the extension direction Z amounting to thesum of ten equal tenth parts, as indicated in FIG. 5B. If the powersemiconductor device 1 is operated in the blocking state, an absolutemaximum AM of electric field strength E caused by the blocking voltageapplied between the first load terminal 11 and the second load terminal12 occurs within six central parts CP of said tenth parts of the totalextension of the semiconductor body 10. For example, the exact positionof the absolute maximum AM can be adjusted by means of the dopantprofile and/or by means of the total extension DZ4 and/or by means ofthe position of the first drift region 104. For example, by shifting theabsolute maximum AM towards a central region of the semiconductor body10, e.g., in proximity to the centre between the first load terminal 11and the second load terminal 12, a cosmic ray robustness of thesemiconductor device 1 may be increased. Further, if implemented intrench architecture, the absolute maximum AM of the electric fieldstrength can also be shifted away from the trench bottoms, which mayfurther increase the robustness of the semiconductor device 1, e.g., dueto lower stresses on the insulator 132, e.g., due to lower trench oxidedegradation, and/or due to a reduction of a risk in avalanche inducedfails, in accordance with one or more embodiments.

The embodiments described above include the recognition that some ofcurrently known IGBTs are rated in such a way that there is asignificant gap between breakdown voltage and a typical DC-link voltage.For instance, a 1200 V-IGBT is operating at a DC-link voltage between600V and 800V or a 6.5 kV-IGBT is operated at a DC-link voltage of3600V. There can be several reasons for this gap: For example, a strayinductance in a power circuit may cause voltage peaks during IGBTturn-off that can trigger strong dynamic avalanche and devicedestruction under overload conditions, e.g., high current, high voltage.Further, cosmic rays may generate secondary high energy particles thatare constantly penetrating the atmosphere. Such secondary particle,e.g., neutrons, can cause the breakdown of the device. There can be anexponential dependency of such a device failure on the applied voltage.In terms of losses, one may want to reduce the voltage rating of theIGBTs for a given application, e.g., use a 900 V-IGBT where nowadays a1200 V-IGBTs is used.

In accordance with one or more embodiments, the power semiconductordevice 1 exhibits an IGBT-configuration, wherein the drift volume of theIGBT-configuration of the power semiconductor device 1 comprises, eitheradditionally or alternatively to the regularly provided drift region,said first drift region 104 having the same conductivity type as thechannel region 102. For example, the power semiconductor device 1exhibits an n-channel IGBT-configuration, wherein the drift volume ofthe n-channel IGBT-configuration of the power semiconductor device 1comprises, either additionally or alternatively to the regularlyprovided n-drift region, said first drift region 104 implemented as ap-doped region, e.g., a p-layer. In another embodiment, the powersemiconductor device 1 exhibits a p-channel IGBT-configuration, whereinthe drift volume of the p-channel IGBT-configuration of the powersemiconductor device 1 comprises, either additionally or alternativelyto the regularly provided p-drift region, said first drift region 104implemented as an n-doped region, e.g., an n-layer.

In accordance with one or more embodiments presented above, the cosmicray robustness can be increased by means of the first drift region 104that comprises the dopants of the second conductivity type, e.g., of thesame conductivity type as the channel region 102. For example, ann-channel IGBT is equipped with a p-drift region instead of or inaddition to an n-drift region, in accordance with one or moreembodiments.

In the above, embodiments pertaining to semiconductor device processingmethods were explained. For example, these semiconductor devices arebased on silicon (Si). Accordingly, a monocrystalline semiconductorregion or layer, e.g., the regions 10, 101, 102, 103, 104, 1041, 105,107, 108 of exemplary embodiments, can be a monocrystalline Si-region orSi-layer. In other embodiments, polycrystalline or amorphous silicon maybe employed.

It should, however, be understood that the semiconductor body 10 andcomponents, e.g., regions 100, 110, 101 and 12 can be made of anysemiconductor material suitable for manufacturing a semiconductordevice. Examples of such materials include, without being limitedthereto, elementary semiconductor materials such as silicon (Si) orgermanium (Ge), group IV compound semiconductor materials such assilicon carbide (SiC) or silicon germanium (SiGe), binary, ternary orquaternary III-V semiconductor materials such as gallium nitride (GaN),gallium arsenide (GaAs), gallium phosphide (GaP), indium phosphide(InP), indium gallium phosphide (InGaPa), aluminum gallium nitride(AlGaN), aluminum indium nitride (AlInN), indium gallium nitride(InGaN), aluminum gallium indium nitride (AlGaInN) or indium galliumarsenide phosphide (InGaAsP), and binary or ternary II-VI semiconductormaterials such as cadmium telluride (CdTe) and mercury cadmium telluride(HgCdTe) to name few. The aforementioned semiconductor materials arealso referred to as “homojunction semiconductor materials”. Whencombining two different semiconductor materials a heterojunctionsemiconductor material is formed. Examples of heterojunctionsemiconductor materials include, without being limited thereto, aluminumgallium nitride (AlGaN)-aluminum gallium indium nitride (AlGaInN),indium gallium nitride (InGaN)-aluminum gallium indium nitride(AlGaInN), indium gallium nitride (InGaN)-gallium nitride (GaN),aluminum gallium nitride (AlGaN)-gallium nitride (GaN), indium galliumnitride (InGaN)-aluminum gallium nitride (AlGaN), silicon-siliconcarbide (SixC1-x) and silicon-SiGe heterojunction semiconductormaterials. For power semiconductor devices applications currently mainlySi, SiC, GaAs and GaN materials are used.

Spatially relative terms such as “under”, “below”, “lower”, “over”,“upper” and the like, are used for ease of description to explain thepositioning of one element relative to a second element. These terms areintended to encompass different orientations of the respective device inaddition to different orientations than those depicted in the figures.Further, terms such as “first”, “second”, and the like, are also used todescribe various elements, regions, sections, etc. and are also notintended to be limiting. Like terms refer to like elements throughoutthe description.

As used herein, the terms “having”, “containing”, “including”,“comprising”, “exhibiting” and the like are open ended terms thatindicate the presence of stated elements or features, but do notpreclude additional elements or features. The articles “a”, “an” and“the” are intended to include the plural as well as the singular, unlessthe context clearly indicates otherwise.

With the above range of variations and applications in mind, it shouldbe understood that the present invention is not limited by the foregoingdescription, nor is it limited by the accompanying drawings. Instead,the present invention is limited only by the following claims and theirlegal equivalents.

What is claimed is:
 1. A bipolar power semiconductor device having asemiconductor body configured to conduct a load current between a firstload terminal and a second load terminal of the power semiconductordevice, the bipolar power semiconductor device further comprising: asource region of a first conductivity type and being electricallyconnected to the first load terminal; a semiconductor channel regionimplemented in the semiconductor body and having a second conductivitytype and separating the source region from a remaining portion of thesemiconductor body; a trench of a first trench type extending in thesemiconductor body along an extension direction and being arrangedadjacent to the semiconductor channel region, the trench of the firsttrench type including a control electrode that is insulated from thesemiconductor body by an insulator, wherein the control electrode isconfigured to control a path of the load current in the semiconductorchannel region; at least one emitter region of the second conductivitytype implemented in the semiconductor body and being electricallyconnected to the second load terminal; wherein the semiconductor bodyfurther comprises: a drift volume having at least a first drift regionof the second conductivity type, wherein a transition between the firstdrift region and a remaining portion of the semiconductor body in theextension direction is arranged below the bottom of the trench, a bufferregion of the first conductivity type being arranged between the driftvolume of the semiconductor body on one side and the emitter region onthe other side, the buffer region having an increasing dopantconcentration for at least 20% of the total extension of the bufferregion along the extension direction, wherein a second drift region ofthe first conductivity type arranged between the first drift region andthe buffer region and having a lower doping concentration than thebuffer region has a total extension along an extension direction of lessthan 80% of the total extension of the semiconductor body along theextension direction.
 2. The bipolar power semiconductor device of claim1, wherein a thickness of the at least one emitter region is less than 1μm.
 3. The bipolar power semiconductor device of claim 1, wherein thefirst drift region is electrically floating.
 4. The bipolar powersemiconductor device of claim 1, wherein the first drift region isarranged in contact with at least a lower section of the trench.
 5. Thebipolar power semiconductor device of claim 4, further comprising: aplurality of trenches arranged in contact with the first drift region.6. The bipolar power semiconductor device of claim 5, wherein theplurality of trenches comprise a trench of a second trench type.
 7. Thebipolar power semiconductor device of claim 6, wherein the trench of thesecond trench type comprises a trench electrode that is electricallyinsulated from the control electrode.
 8. The bipolar power semiconductordevice of claim 7, wherein the trench electrode of the trench of thesecond trench type is electrically connected to the first load terminal.9. The bipolar power semiconductor device of claim 1, wherein the firstdrift region does not extend outside of an active cell field.
 10. Thebipolar power semiconductor device of claim 1, wherein the first driftregion adjoins the buffer region.
 11. The bipolar power semiconductordevice of claim 1, wherein the first drift region is directly connectedto the semiconductor channel region.
 12. The bipolar power semiconductordevice of claim 1, wherein the semiconductor body further comprises: abarrier region of the first conductivity type between the semiconductorchannel region and the first drift region.
 13. A bipolar powersemiconductor device having a semiconductor body comprising: a sourceregion of a first conductivity type; a semiconductor channel regionimplemented in the semiconductor body and having a second conductivitytype and separating the source region from a remaining portion of thesemiconductor body; a trench extending in the semiconductor body alongan extension direction and being arranged adjacent to the semiconductorchannel region; an emitter region of the second conductivity typeimplemented in the semiconductor body; a drift volume having a firstdrift region of the second conductivity type, wherein a transitionbetween the first drift region and a remaining portion of thesemiconductor body in the extension direction is arranged below thebottom of the trench; a buffer region of the first conductivity typebeing arranged between the drift volume and the emitter region, thebuffer region having an increasing dopant concentration for at least 20%of the total extension of the buffer region along the extensiondirection; and a second drift region of the first conductivity typearranged between the first drift region and the buffer region and havinga lower doping concentration than the buffer region and a totalextension along an extension direction of less than 80% of the totalextension of the semiconductor body along the extension direction. 14.The bipolar power semiconductor device of claim 13, wherein a thicknessof the emitter region is less than 1 μm.
 15. The bipolar powersemiconductor device of claim 13, wherein the first drift region iselectrically floating.
 16. The bipolar power semiconductor device ofclaim 13, wherein the first drift region is arranged in contact with atleast a lower section of the trench.
 17. The bipolar power semiconductordevice of claim 13, further comprising: a plurality of trenches arrangedin contact with the first drift region.
 18. The bipolar powersemiconductor device of claim 13, wherein the first drift region adjoinsthe buffer region.
 19. The bipolar power semiconductor device of claim13, wherein the first drift region is directly connected to thesemiconductor channel region.
 20. The bipolar power semiconductor deviceof claim 13, further comprising: a barrier region of the firstconductivity type between the semiconductor channel region and the firstdrift region.